Lighting fixture providing variable CCT

Abstract

The present disclosure relates to a lighting fixture that is capable of providing white light over an extended range of correlated color temperatures.

What is claimed is: 
     
       1. A lighting fixture comprising:
 at least one wavelength converted LED of a first color with a first color point on a CIE 1976 chromaticity diagram, the first color point being defined by first color point coordinates (u′, v′) on the CIE 1976 chromaticity diagram, at least one wavelength converted LED of a second color with a second color point on the CIE 1976 chromaticity diagram, the second color point being defined by second color point coordinates (u′, v′) on the CIE 1976 chromaticity diagram, and at least one LED of a third color with a third color point on the CIE 1976 chromaticity diagram; and 
 a driver module comprising:
 a control circuitry; and 
 at least one DC-DC converter, wherein the driver module is configured to:
 generate a first current for the at least one wavelength converted LED of the first color, a second current for the at least one wavelength converted LED of the second color, and a third current for the at least one LED of the third color; 
 receive both correlated color temperature information indicative of a desired correlated color temperature and dimming information indicative of a desired dimming level; 
 receive temperature information indicative of a temperature; 
 select reference control signals for the first, second, and third currents based on the desired correlated color temperature; 
 apply a tuning offset to each of the reference control signals, wherein the tuning offset is a multiplier; 
 adjust the reference control signals for the first, second, and third currents based on the dimming information, the correlated color temperature information, and the temperature information; 
 adjust the first, second, and third currents based on the adjusted reference control signals for the first, second, and third currents, such that light emitted from the at least one wavelength converted LED of the first color, light emitted from the at least one wavelength converted LED of the second color and light emitted from the at least one LED of the third color combine to form a light with the desired correlated color temperature and corresponding to the desired dimming level while maintaining the desired correlated color temperature such that if an intensity corresponding to the desired dimming level changes or the temperature changes, the desired correlated color temperature remains unchanged; and 
 
 wherein a difference in v′ of the first color point coordinates and the second color point coordinates is greater than 0.033. 
 
 
     
     
       2. The lighting fixture of  claim 1  wherein the difference in v′ of the first color point coordinates and the second color point coordinates is greater than 0.0400 and less than 0.1500. 
     
     
       3. The lighting fixture of  claim 1  wherein the difference in v′ of the first color point coordinates and the second color point coordinates is greater than 0.0500 and less than 0.1500. 
     
     
       4. The lighting fixture of  claim 1  wherein the driver module is configured to provide the first, second, and third currents such that the light emitted from the at least one wavelength converted LED of the first color, the light emitted from the at least one wavelength converted LED of the second color, and the light emitted from the at least one LED of the third color combine to form white light with a color point that falls along a black body locus. 
     
     
       5. The lighting fixture of  claim 4  wherein the color point that falls along the black body locus is within a five-step MacAdam ellipse of the black body locus. 
     
     
       6. The lighting fixture of  claim 4  wherein the color point that falls along the black body locus is within a four-step MacAdam ellipse of the black body locus. 
     
     
       7. The lighting fixture of  claim 4  wherein the driver module is further configured to variably control ratios of the first, second, and third currents such that a correlated color temperature for the white light is adjustable along the black body locus from about 2700 K to about 5700 K. 
     
     
       8. The lighting fixture of  claim 4  wherein the driver module is further configured to variably control ratios of the first, second, and third currents such that a correlated color temperature for the white light is adjustable along the black body locus from about 3000 K to about 5000 K. 
     
     
       9. The lighting fixture of  claim 4  wherein the driver module is further configured to variably control ratios of the first, second, and third currents such that a correlated color temperature for the white light is adjustable along the black body locus from about 3000 K to about 4000 K. 
     
     
       10. The lighting fixture of  claim 1  wherein the at least one wavelength converted LED of the first color is a blue-shifted yellow LED, the at least one wavelength converted LED of the second color is a blue-shifted yellow LED, and the at least one LED of the third color is a red LED. 
     
     
       11. The lighting fixture of  claim 10  wherein the at least one LED of the third color is not wavelength converted. 
     
     
       12. The lighting fixture of  claim 1  wherein the at least one wavelength converted LED of the first color is a blue-shifted green LED, the at least one wavelength converted LED of the second color is a blue-shifted green LED, and the at least one LED of the third color is a red LED. 
     
     
       13. The lighting fixture of  claim 1  wherein the at least one wavelength converted LED of the first color consists essentially of a string of wavelength converted LEDs of essentially the first color; the at least one wavelength converted LED of the second color consists essentially of a string of wavelength converted LEDs of essentially the second color; and the at least one LED of the third color consists essentially of a string of LEDs of essentially the third color. 
     
     
       14. The lighting fixture of  claim 13  wherein the driver module is configured to provide the first, second, and third currents such that light emitted from the string of wavelength converted LEDs of essentially the first color; light emitted from the string of wavelength converted LEDs of essentially the second color; and light emitted from the string of LEDs of essentially the third color combine to form white light with a color point that falls along a black body locus. 
     
     
       15. The lighting fixture of  claim 14  wherein the driver module is further configured to variably control ratios of the first, second, and third currents such that a correlated color temperature for the white light is adjustable along the black body locus from about 3000 K to about 5000 K. 
     
     
       16. The lighting fixture of  claim 15  wherein the at least one wavelength converted LED of the first color is a blue-shifted LED, the at least one wavelength converted LED of the second color is a blue-shifted LED, and the at least one LED of the third color is a red LED. 
     
     
       17. The lighting fixture of  claim 1  wherein the driver module is further configured to variably control ratios of the first, second, and third currents such that the desired correlated color temperature for white light is adjustable along a black body locus from about 3000 K to about 5000 K. 
     
     
       18. The lighting fixture of  claim 17  wherein the at least one wavelength converted LED of the first color consists essentially of a string of wavelength converted LEDs of essentially the first color; the at least one wavelength converted LED of the second color consists essentially of a string of wavelength converted LEDs of essentially the second color; and the at least one LED of the third color consists essentially of a string of LEDs of essentially the third color. 
     
     
       19. The lighting fixture of  claim 4  wherein the white light has a color rendering index of greater than 90. 
     
     
       20. The lighting fixture of  claim 1  wherein the correlated color temperature information is indicative of a desired correlated temperature on a black body locus for white light.